Tool lift mechanism

ABSTRACT

The present application relates to a lifting apparatus comprising a first member and a second member; a lifting mechanism coupled to said first member adapted to move said first member towards said second member; and a third member coupled to said first member, the third member slideably moveable through said second member when said first member is moved towards said second member. When a predetermined compressive force is applied to said third member, a latching mechanism responds by latching said second member to said third member, such that when a further compressive force is applied to said third member, said first member and lifting mechanism are isolated from said further compressive force.

The invention relates to a lifting apparatus, particularly in the context of a tray sealing machine. Here, the term “tray” means any container having an upwardly facing opening to which a film is to be heat sealed.

In the food industry, it is common to package food items in heat sealed trays. Conventionally, trays are transported along a conveyer and filled with the desired food items. The tray is then fed, typically with a plurality of other trays, to a tray sealing machine.

The tray sealing machine typically comprises a lower tool half on which the tray(s) is positioned, and an upper tool half. The lower tool half is lifted towards the upper tool half via a lifting mechanism, and the upper and lower tool halves are clamped together to generate an air tight seal. The lower tool half has an ejector plate which lowers the trays into a recess as the lower tool half is lifted towards the upper tool half. The sealing process can then take place.

Lifting mechanisms using a motor-driven spindle to lift the lower tool half are known in the art. However, when the sealing process takes place, a large force is placed on the lifting spindle, much larger than the load placed on the spindle during lifting of the lower tool half. This large force placed on the lifting spindle could cause it to buckle, having serious consequences not only for the output of the tray sealing machine, but also for safety.

In order to overcome this problem, such a spindle is commonly manufactured with a relatively large diameter to improve its strength in order to protect against buckling. This increases cost since more material is required for the larger spindle, and a more powerful motor is needed in order to drive it.

Alternatively or in addition, a large high power electromechanical brake may be used to reduce the forces experienced by the spindle. However, this also increases cost due to the increased complexity and power consumption.

What is needed in the art is a lifting mechanism for a tray sealing machine that prevents the problem of the lifting mechanism buckling or being damaged under the high loads caused by the sealing process, without compromising on the efficiency, speed and cost of the tray sealing machine.

US2009/0288365 discloses a packaging machine having a lifting unit. The lifting unit has preferably two spindles, each attached to a lifting plate by a spindle bearing. Two guiding rods are also mounted on each lifting plate, which are connected at their upper end to a lower tool half. When the lower tool half has been raised to the desired position by the spindles, brakes independently mounted to each guiding rod are actuated, thus avoiding undesired lowering of the lifting unit during operation. As the lifting plates are mounted via the spindle bearings, the spindles are kept stationary, and are thus exclusively stressed by tension, excluding the risk of buckling.

However, in the disclosure of US2009/0288365, the spindles are still subject to large forces, even if they are in tension. The spindle will have to be designed to account for these forces. Moreover, the spindle bearings may be damaged by being subject to said forces.

In accordance with the present invention, a lifting apparatus is provided comprising; a first member and a second member; a lifting mechanism coupled to said first member adapted to move said first member towards said second member; a third member coupled to said first member and slideably moveable through said second member when said first member is moved towards said second member, and a latching mechanism wherein; when a predetermined compressive force is applied to said third member, the latching mechanism responds by latching said second member to said third member, such that when a further compressive force is applied to said third member, said first member and lifting mechanism are isolated from said further compressive force.

A key advantage of this invention is that when the further compressive force is applied to the third member, this force is transferred through the latching mechanism to the second member. This isolates the first member and, importantly, the lifting mechanism, from said further compressive force. This means that the lifting mechanism does not have to be specifically designed to take into account the further force, making manufacture simpler, and reducing the amount of material required.

Further, the latching mechanism advantageously latches the second member to the third member automatically on application of the predetermined compressive force. Other automatic latching mechanisms are envisaged. For example, a pressure sensor could be used to detect when the lower and upper tool halves are in contact, and an electronic system used to initiate the latches. The automatic nature of the latching mechanism allows the lifting mechanism of the present invention to be used without supervision.

Preferably, the latching mechanism comprises a spring mounted between said third member and said first member wherein in use said spring is compressed on application of said compressive force to said third member, and said predetermined compressive force corresponds to a predetermined point in the spring's compression. Alternatively, a compressible fluid could be used instead of a spring.

In a preferred embodiment, the latching mechanism comprises a latch cam plate having a shaped portion, said latch cam plate fixedly coupled to said first member, and wherein the movement of said first member towards said second member causes said shaped portion to guide a latch so as the latch engages with a protruding potion on said third member. Other latching mechanisms are envisaged, for example electromagnetically actuated latches.

In a preferred embodiment, the first member is a plate and said third member is elongate and coupled to said first member so as to project along the direction of movement of said first member.

Preferably, the lifting mechanism is a rotateable lifting screw coupled to the first member in such a manner that rotation of said lifting screw causes movement of said first member in a plane substantially perpendicular to the rotation axis of said lifting screw.

This advantageously means that the lifting screw remains stationary as the lifting plate is raised, allowing for increased ease of installation as movement of the lifting screw does not have to be accounted for.

It will however be appreciated by those skilled in the art that other lifting mechanisms may be used. For example, the first member may be moved towards the third member by means of pistons or a pulley system.

In a preferred embodiment, the lifting apparatus further comprises one or more third members. For example, in one embodiment a second third member is also coupled to said first member via a spring, and is slideably movable through a second member. In this embodiment, the second third member provides increased support for an item to be lifted by the lifting apparatus, where the item is supported by the third members.

In one embodiment, the lifting screw and the or each third member are substantially parallel.

The lifting apparatus may be included in a tool lift apparatus, the tool lift apparatus further comprising a lower tool half mounted to the distal end of the or each third member such that, in use, movement of the first member moves said lower tool half towards an upper tool half, and wherein said predetermined compressive force is due to said lower tool half and said upper tool half contacting.

In one embodiment, the tool lift apparatus is employed in a tray sealing machine, where the further compressive force is due to a sealing process taking place when the upper and lower tool halves are in contact and form an air-tight seal. However, the lifting apparatus may be employed in other instances apart from tray sealing machines, such as thermoformer machines and press tooling.

In one embodiment, such a tool lift apparatus further comprises a second lifting apparatus, wherein said lower tool half is mounted to the distal end of the or each third member of the first and second lifting apparatuses, and further wherein the first and second lifting apparatuses are operated in synchrony.

The lower tool half of such an embodiment thus advantageously has greater support as it is supported by two lifting apparatuses. Such a tool lift apparatus may be utilised in a single lane tray sealing machine.

In an alternative embodiment, the tool lift apparatus further comprises a second lifting apparatus and a second lower tool half mounted to the distal end of the or each third member of said second lifting apparatus, and wherein said first and second lifting apparatuses are operated independently. There may also be an independent upper tool half corresponding to the second lower tool half.

This embodiment provides increased flexibility in the use of the tool lift apparatus, especially when used in a dual lane tray sealing machine for instance. For example, one lane may be used for large trays that are sealed three at a time, and the second lane used to seal small trays that are sealed four at a time and at a faster rate. The independent lifting apparatuses and tool halves allow for maximum flexibility in such a situation, increasing throughput and efficiency of the tray sealing machine.

Embodiments of the present invention will now be described and contrasted with the prior art with reference to the following drawings in which:

FIG. 1 is a schematic side view partly in section of a lifting apparatus according to an embodiment of the present invention with a lifting plate in a lower position;

FIG. 2 is a view similar to FIG. 1, but showing the lifting plate in an upper position;

FIG. 3 is a view of a lifting apparatus of the present invention in use in a single lane tray sealing machine;

FIG. 4 is a view of a lifting apparatus of the present invention in use in a dual lane tray sealing machine;

FIG. 5 a is a staggered cross-section of the lifting apparatus of FIGS. 1 and 2, showing the latching mechanism in more detail;

FIG. 5 b is another staggered cross-section of the lifting apparatus of FIGS. 1 and 2, showing the latching mechanism in more detail;

FIG. 6 a is another staggered cross-section of the lifting apparatus of FIGS. 1 and 2, showing the latching mechanism in more detail; and

FIG. 6 b is a further staggered cross-section of the lifting apparatus according to FIGS. 1 and 2, showing the latching mechanism in more detail.

In the following description, directional terms such as “raised”, “lowered”, “upper”, “lower” etc. are used for clarity in explaining the figures and are not intended to be limiting.

Considering first FIG. 1, there is shown a lifting apparatus comprising two pillars 1 a, 1 b attached to a lifting plate 7. In this embodiment, each pillar 1 is slideably moveable through a housing structure 9 surrounding said pillar, and each housing structure 9 is mounted on a stationary upper plate 11. Other means of mounting the housing structures are envisaged.

The pillars may be circular or square in cross-section. Other cross-sectional shapes may be used.

In the following description, a single pillar la will be referred to for ease of understanding.

The lifting plate 7 is raised towards the upper plate 11 by means of a lifting screw 2 rotateably mounted via bearings 2 a in the upper plate 11 and received in a screw threaded bush 2 b in the lifting plate 7. A gear 3 b is fixed to the upper end of the screw and is connected to a motor 3 by tooth belt 3 a. The lifting screw 2 is rotated by said motor 3, causing the lifting plate 7 to move upwards towards plate 11 in a plane substantially perpendicular to the axis of rotation.

As will be appreciated by those skilled in the art, although FIGS. 1 and 2 show the lifting screw 2 located between the two pillars 1 a, 1 b, with the pillars and lifting screw substantially parallel, this is not necessarily the case. The lifting apparatus of the present invention may contain any number of pillars.

As seen in FIG. 2, upon rotation of the lifting screw 2, the lifting plate 7 is moved relative to the lifting screw 2. This advantageously simplifies installation of the lifting mechanism, since the lifting screw 2 remains stationary with respect to the motor 3 and upper plate 11, and thus the installation does not need to take into account movement of the lifting screw. Other means of raising the lifting plate 7 are envisaged, for example hydraulic pillars mounted beneath the plate in order to push it upwards towards upper plate 11.

In an embodiment of the invention, the lifting apparatus as depicted in FIG. 1 is used in a tray sealing machine. In such an embodiment, trays to be sealed are loaded onto a lower tool half (20 in FIG. 3) attached to the upper end of each pillar 1 a, 1 b. As the lifting plate 7 is raised, the lower tool half is raised towards an upper tool half (not shown). The lower tool half has an ejector plate which lowers the trays into a recess as the lower tool half is raised towards the upper tool half. The lower and upper tool halves come into contact and form an air tight seal. The upper tool half is heated so as to seal the film to the tray.

The two-pillar lifting apparatus depicted in FIGS. 1 and 2 is referred to as a module. In one embodiment, depicted in FIG. 3, a single lane tray sealing machine 100 comprises two modules 101, 102 in lateral proximity with a predefined pitch between the four pillars. Both modules 101, 102 are connected to a common drive motor 3 via a tooth belt, and all four pillars are driven together, raising the lower tool half 20 of the tray sealing machine towards the upper tool half (not shown).

In another embodiment seen in FIG. 4, two modules 101, 102 may be used in a dual-lane tray sealing machine 200. In this embodiment each module has a separate drive motor 3 and separate tooth belts. This allows each module to operate independently, allowing two separate lower tool halves 20 a, 20 b to operate independently. There may be a common upper tool half (not shown) for both lower tool halves 20 a, 20 b, or each lower tool half may have a corresponding independent upper tool half. The modules 101, 102 are the same as those seen in FIG. 3 but are reversed from the single lane application. The pitch between the modules can be altered to suit the particular dual lane application due to the asymmetric design of the modules.

As the lifting apparatus of the present invention can be used in a dual lane situation with independent tray sealing machine lower tool halves 20 a, 20 b, this advantageously allows different tray sizes to be packaged and sealed concurrently, increasing throughput. Enabling the use of independently operable lower tool halves also allows different numbers of trays to be sealed at a time on each lane. For example, two trays can be sealed at a time on one lane, and three at a time on the other. In this way, flexibility of tray sealing is further increased.

It is envisaged that a lower tool half of a tray sealing machine may be supported by any number of pillars. For example, one pillar may be used to support a lower tool half.

For ease of understanding, the following description will refer to a single module.

The sealing load placed on the lifting mechanism is far greater than the lifting load caused by raising the lower tool half, as the sealing process forces the upper and lower tool halves apart. The lifting apparatus of the present invention allows the lifting screw 2 and motor 3 to be isolated from the sealing load, as described below. This means that the lifting screw 2 does not need to be as robust as in the prior art, and can thus have a relatively small diameter, advantageously minimising manufacturing cost and mechanism size. Similarly, motor 3 and any electro-mechanical brake can be downsized as it does not have to drive a large lifting screw 2 or lifting mechanism designed to withstand the sealing load.

When the lower tool half first makes contact with the upper tool half, motor 3 continues to rotate the lifting screw 2, raising the lifting plate 7 upwards towards the upper plate 11. As seen in FIGS. 1 and 2, a spring housing 13 is attached to the underside of lifting plate 7, said spring housing 13 housing two springs 6 coupled to the spring housing 13 and pillar 1 a. A corresponding spring housing 13 with two springs 6 is provided for pillar 1 b, however for ease of understanding the lifting apparatus is described with reference to pillar 1 a in the following description.

As motor 3 continues to drive lifting screw 2 when the upper and lower tool halves are in contact, pillar 1 a remains stationary but lifting plate 7 continues to move upwards towards plate 11, thus compressing springs 6. In the present embodiment the two springs are identical and so compress at the same rate, although different springs may be used. At a predetermined point in the compression of the springs, a latching mechanism responds by latching the housing structure 9 to the pillar 1 a. The latching mechanism comprises latches 4 located on the housing structure 9 which engage with each protruding portion 12 on the pillar 1 a. The motor 3 stops at a predetermined position set in the motor control unit (not shown), but could equally be controlled by a sensor or switch attached to the mechanism.

In the embodiment shown in FIGS. 1 and 2, the spring housings 13 contain two springs each. However, this is not necessarily the case and any number of springs may be used, for example a single spring. Alternatively, a hydraulic system using a compressible fluid may be implemented instead of the use of a spring(s).

The housing structure 9 and spring(s) 6 are not limited to their described position. For example, the spring housing 13 could be mounted on the upper side of lifting plate 7, thus placing the spring(s) 6 under tension as the lifting plate 7 continues to rise when the upper and lower tool halves first come into contact.

As the pillars are now coupled to the housing structures 9 via latches 4, the load placed on pillars 1 due to the sealing process is transferred through latches 4 to the housing structures 9. This therefore advantageously isolates the lifting screw 2 and motor 3 from these high loads as the pillars 1 are coupled to lifting plate 7 via spring 6.

The latching mechanism will now be described in more detail with reference to FIGS. 5 a, 5 b, 6 a and 6 b. The latching mechanism comprises latches 4 and spring 6 as described above, as well as latch cam plate 5 and cam follower rollers 10. Its operation will be described below.

FIGS. 5 a, 5 b, 6 a and 6 b are staggered cross-section diagrams taken along the axis x-x′. FIG. 5 a shows a cross section taken through a pillar 1 a, and FIG. 5 b shows a cross section taken through latch cam plate 5, both before the latches 4 are engaged. The two views are of the same pillar 1 a and have been shown side by side for ease of comparison and do not represent two independent pillars. FIGS. 6 a and 6 b show the equivalent views when the latches 4 are engaged.

Considering first FIGS. 5 b and 6 b, latch cam plate 5 (hereafter referred to as latch plate) fixedly coupled to lifting plate 7 is moved towards latches 4 as the lifting plate 7 is raised. Latches 4 comprise two complementary structures 4 a and 4 b facing each other as seen in FIGS. 5 b and 6 b. Each complementary structure 4 a, 4 b contains a cam follower roller 10 (hereafter referred to as roller).

When the lower tool half comes into contact with the upper tool half, as explained above, lifting plate 7 continues to rise and compresses spring(s) 6. The latch plate 5, coupled to lifting plate 7, will come into contact with the rollers 10, specifically at the shaped portion 14 of the latch plate. The spring(s) 6 will continue to compress until, at a predetermined compression point, the spring(s) becomes compressed enough to positively drive the latch plate 5 further upwards, forcing the rollers 10 along guided portion 14 into the recessed portion 16 of the latch plate 5.

This causes the complementary structure 4 a and 4 b to move inwards towards each other, engaging with the protruding portions 12 on the pillar 1, as seen in FIGS. 5 a and 6 a. The motor 3 is stopped on engagement of the latches with the protruding portions and thus the lifting plate 7 becomes stationary. The sealing process can then occur, transferring the high loads through the latches 4 to the housing structure 9, thus isolating the lifting screw 2 and motor 3 from said loads.

On completion of the sealing process, the motor 3 is driven in the reverse direction, thus causing the lifting plate 7 to lower away from the upper plate 11. This places the springs 6 under tension, and at a predetermined point in the extension of the springs, the rollers 10 are released from the recessed portion 16 in the latch plate 5, and the shaped portion 14 of the latch plate positively drives the complementary structures 4 a and 4 b back to their original position. The complementary structures are retained in their original position by the proximity of the pillar passing the latches 4, as seen in FIG. 5 a. This releases protruding portion 12 on the pillar 1.

As seen in FIGS. 1 and 2, although two protruding portions 12 are shown on opposing sides of pillar one or more protruding portions and corresponding latches 4 could be used. Similarly, although two latch plates 5 are shown on the lifting plate 7 on opposing sides of pillar 1 a, a single latch plate 5 may be used, or more then two latch plates may be used.

Other latching mechanisms are envisaged. For example, electronically actuated latches could be engaged at the desired time using a control unit.

When the lifting plate 7 is in its lower position, the sealed trays can be transported away from the lower tool half, for example by gripper arms and a conveyer, and unsealed trays to be sealed can be transported on to the lower tool half for the process to repeat.

The lifting apparatus is not restricted to the described embodiment. For example, the upper tool half may be moved towards a stationary lower tool half. It is also envisaged that the lifting mechanism of the present invention can be used in conjunction with a twin lane device, an example of which being the QX-1100 manufactured by Ishida Europe Limited of Birmingham, United Kingdom.

Although described with relation to a tray sealing machine, the lifting apparatus of the present application can be used in other scenarios and apparatuses. 

1. A lifting apparatus connectable to a tray sealing tool, the lifting apparatus comprising; a first member and a second member; a lifting mechanism coupled to said first member adapted to move said first member towards said second member; a third member coupled to said first member and slideably moveable through said second member when said first member is moved towards said second member, a distal end of the third member, with respect to the first member, being connectable to a lower tool half of a tray sealing tool such that when said first member is moved towards said second member, the lower tool half is moved towards an upper tool half of the sealing tool, the lifting apparatus further comprising a latching mechanism, and wherein; when a predetermined compressive force is applied to said third member, due to the lower tool half contacting the upper tool half, said predetermined compressive force actuates the latching mechanism to latch said second member to said third member, such that when a further compressive force is applied to said third member due to sealing forces in the tray sealing tool, said first member and lifting mechanism are isolated from said further compressive force.
 2. The lifting apparatus of claim 1, wherein the latching mechanism comprises a spring mounted between said third member and said first member wherein in use said spring is compressed on application of said compressive force to said third member, and said predetermined compressive force corresponds to a predetermined point in the spring's compression.
 3. The lifting apparatus of claim 1, wherein the latching mechanism comprises a latch cam plate having a shaped portion, said latch cam plate fixedly coupled to said first member, and wherein the movement of said first member towards said second member causes said shaped portion to guide a latch so as the latch engages with a protruding potion on said third member.
 4. The lifting apparatus of claim 1, wherein said first member is a plate.
 5. The lifting apparatus of claim 1, wherein said third member is elongate and coupled to said first member so as to project along the direction of movement of said first member.
 6. The lifting apparatus of claim 1, wherein said lifting mechanism is a rotatable lifting screw coupled to the first member in such a manner that rotation of said lifting screw causes movement of said first member in a plane substantially perpendicular to the rotation axis of said lifting screw.
 7. The lifting apparatus of claim 1, further comprising one or more third members.
 8. The lifting apparatus of claim 5, wherein the lifting screw and the or each third member are substantially parallel.
 9. A tool lift apparatus comprising the lifting apparatus of claim 1, and further comprising; a lower tool half mounted to the distal end of the or each third member such that, in use, movement of the first member moves said lower tool half towards an upper tool half, and wherein; said predetermined compressive force is due to said lower tool half and said upper tool half contacting.
 10. The tool lift apparatus of claim 9, further comprising a second lifting apparatus, and wherein said lower tool half is mounted to the distal end of the or each third member of the first and second lifting apparatuses, and further wherein the first and second lifting apparatuses are operated in synchrony.
 11. The tool lift apparatus of claim 9, further comprising a second lifting apparatus and a second lower tool half mounted to the distal end of the or each third member of said second lifting apparatus, and wherein said first and second lifting apparatuses are operated independently.
 12. The tool lift apparatus of claim 11, further comprising a second upper tool half corresponding to the second lower tool half
 13. The tool lift apparatus of claim 9, wherein said further compressive force is caused by a process performed when said lower tool half and said upper tool half are in contact.
 14. A traysealing machine comprising the tool lift apparatus of claim
 9. 15. The traysealing machine of claim 14, wherein the upper tool half contains a heated plate.
 16. The traysealing machine of claim 14, wherein the lower tool half is adapted to support one or more trays to be sealed. 